Kinetic Modeling of Oxidation of Antibacterial Agents by Manganese Oxide

Abstract

Several groups of popular antibacterial agents (i.e., phenols, fluoroquinolones, aromatic N-oxides, and tetracyclines) were demonstrated in earlier studies to be highly susceptible to oxidation by manganese oxides, a common oxidant in soils. However, because of the high complexity, the reaction kinetics were not fully characterized. A mechanism-based kinetic model has now been developed to successfully describe the entire range of kinetic data for a total of 21 compounds of varying structural characteristics (with R2 > 0.93). The model characterizes the reaction kinetics by two independent parameters, the reaction rate constant (k) and total reactive surface sites (S(rxn)). The model fitting indicates that the reaction kinetics of antibacterials with MnO2 are controlled by either the rate of surface precursor complex formation (for tetracyclines) or by the rate of electron transfer within the precursor complex (for phenols, fluoroquinolones, and aromatic N-oxides). The effect of reactant concentration, pH, and cosolutes on the reaction kinetics was evaluated and correlated to kand S(rxn). All the trends are consistent with the proposed rate-limiting steps. This new model improves the ability to quantitatively evaluate the kinetics of oxidative transformation of organic contaminants by manganese oxides in well-defined systems.

MnO2 AND MnO2/TiO2 MEDIATED, PERSULPHATE ENHANCED PHOTOCATALYSIS FOR THE REMOVAL OF INDIGO CARMINE DYE POLLUTANT FROM WATER

“…It is also possible that the heterogeneous degradation in the presence of MnO2 involves the formation of precursor complex between the dye and surface bound Mn. 46 Electrons from the activated dye move to the Mn(IV) on the surface of MnO2. Consequently, the dye undergoes oxidative degradation.…”

Degradation of tetracycline in aqueous medium by electrochemical method

“…5(b)). The electrochemical oxidation of tetracycline would lead to the production of intermediates, which may also simultaneously be degraded on the anode by direct electron transfer and by hydroxyl radicals according to the reaction [2] . The decrease in rate of tetracycline degradation may be due to the competitive reaction of the daughter compounds with the parent compound on the anode.…”

“…[1] Among various pharmaceutical compounds, antibiotics are of special concern because of their extensive use in human and veterinary medicine and their potential to promote growth of resistant bacteria and pose adverse health effects to humans. [1,2] As a result of their antibacterial nature, antibiotic residues cannot be effectively destructed by traditional biological methods. [3] Although antibiotics could be removed by physical processes such as granular activated carbon filtration, [4] they were just transferred to another medium (carbon), which requires further treatment and disposal.…”

Fate of Pesticides in Soils: Toward an Integrated Approach of Influential Factors

“…The oxidation reaction begins with the formation of a precursor complex between the pollutant and the surface-bound metallic species, followed by electron transfer within the complex and release of an organic cationic radical, that will evolve to an oxidized form or bind to a vicinal reactive species. Through the development of a mechanism-based kinetic model, Zhang et al (2008) demonstrated that environmental factors may affect either the reaction kinetics of MnO 2 -pollutant complex formation or the rate of electron transfer, directly or through action on the reactive surface sites. Among solutes, Mn(II) presents the strongest inhibitory effect, followed by other divalent cations as Ca 2+ .…”